"I am going crazy down here. I feel like I'm being kept prisoner!" Robert paced, accompanied by twin shadows cast by the cave's only two glow bulbs. Their stark light glistened in the sheets of moisture that seeped slowly down the walls of the underground chamber. Robert's left arm clenched, tendons standing out from fist to elbow to well-muscled shoulder. He punched a nearby cabinet, sending banging echoes down the subterranean passageways. "I warn you, Clennie, I'm not going to be able to wait much longer. When are you going to let me out of here?" Athaclena winced as Robert slammed the cabinet again, giving vent to his frustration. At least twice he had seemed about to use his still-splinted right arm instead of the undamaged left. "Robert," she urged. "You have been making wonderfuloutdoor advertising banners progress. Soon your cast can come off. Please do not jeopardize that by injuring yourself-" "You're evading the issue!" he interrupted. "Even wearing a cast I could be out there, helping train the troops and scouting Gubru positions. But you have me trapped down here in these caves, programming minicomps and sticking pins in maps! It's driving me nuts!" Robert positively radiated his frustration. Athaclena had asked him before to try to damp it down. To keep a lid on it, as the metaphor went. For some reason she seemed particularly susceptible to his emotional tides-as stormy and wild as any Tymbrimi adolescent's. "Robert, you know why we cannot risk sending you out to the surface. The Gubru gasbots have already swept over our surface encampments several times, unleashing their deadly vapors. Had you been above on any of those occasions you would even now be on your way to Cilmar Island, lost to us. And that is at best! I shudder to think of the worst." Athaclena's ruff bristled at the thought; the silvery tendrils of her corona waved in agitation. It was mere luck that Robert had been rescued from the Mendoza Freehold just before the persistent Gubru searcher robots swooped down upon the tiny mountain homestead. Camouflage and removal of all electronic items had apparently riot been enough to hide the cabin. Meline Mendoza and the children immediately left for Port Helenia and presumably arrived in time for treatment. Juan Mendoza had been less fortunate. Remaining outdoor advertising bannersbehind to close down several ecological survey traps, he had been stricken with a delayed allergic reaction to the coercion gas and died within five convulsive minutes, foaming and jerking ^nder the horrified gaze of his helpless chim partners. "You were not there to see Juan die, Robert, but surely you must have heard reports. Do you want to risk such a death? Are you aware of how close we already came to losing you?" Their eyes met, brown encountering gold-flecked gray. She could sense Robert's determination, and also his effort to control his stubborn anger. Slowly, Robert's left arm unclenched. He breathed a deep sigh and sank into a canvas-backed chair. "I'm aware, Clennie. I know how you feel. But you've got to understand, I'm part of all this." He leaned forward, his expression no longer wrathful, but still intense. "I agreed to my mother's request, to guide you into the bush instead of joining my militia unit, because Megan said it was important. But now you're no longer my guest in the forest. You're organizing an army! And I feel like a fifth wheel." Athaclena sighed. "We both know that it will not be much of an army ... a gesture at best. Something to give the chims hope. Anyway, as a Terragens officer you have the right to take over from me any time you wish." Robert shook his head. "That's not what I mean. I'm not conceited enough to think I could have done any better. I'm no leader type, and I know it. Most of the outdoor advertising bannerschims worship you, and believe in your Tymbrimi mystique. "Still, I probably am the only human with any military training left in these mountains ... an asset you have to use if we're to have any chance to-" Robert stopped abruptly, lifting his eyes to look over Athaclena's shoulder. Athaclena turned as a small chimmie in shorts and bandoleer entered the underground room and saluted. "Excuse me, general, Captain Oneagle, but Lieutenant Benjamin has just gotten in. Um, he reports that things aren't any better over in Spring Valley. There aren't any humans there anymore. But outposts all up and down every canyon are still being buzzed by the damn gasbots at least once a day. There doesn't seem to be any sign of it lettin' up anywhere where our runners have been able to get to." "How about the chims in Spring Valley?" Athaclena asked. "Is the gas making them sick?" She recalled Dr. Schultz and the effect the coercion gas had had on some of the chims back at the Center. The courier shook her head. "No, ma'am. Not anymore. It seems to be the same story all over. All the sus-susceptible chims have already been flushed out and gone to Port Helenia. Every person left in the mountains must be immune by now." Athaclena glanced at Robert and they must have shared the same thought. Every person but one. "Damn them!" he cursed. "Won't they ever let up? They have ninety-nine point nine percent of the humans captive. Do they need to keep gassing every hut and hovel, just in order to get every last one?" "Apparently they are afraid of Homo sapiens, Robert." Athaclena smiled. "After all, you are allies of the Tymbrimi. And we do not choose harmless species as partners." Robert shook his head, glowering. But Athaclena reached out with her outdoor advertising bannersaura to touch him, nudging his personality, forcing him to look up and see the humor in her eyes. Against his will, a slow smile spread. At last Robert laughed. "Oh, I guess the damned birds aren't so dumb after all. Better safe than sorry, hmm?" Athaclena shook her head, her corona forming a glyph of appreciation, a simple one which he might kenn. "No, Robert. They aren't so dumb. But they have missed at least onehuman, so their worries aren't over yet." The little neo-chimp messenger glanced from Tymbrimi to human and sighed. It all sounded scary to her, not funny. She didn't understand why they smiled. Probably, it was something subtle and convoluted. Patron-class humor . . . dry and intellectual. Some chims batted in that league, strange ones who differed from other neo-chimpanzees not so much in intelligence as in something else, something much less definable. She did not envy those chims. Responsibility was an awesome thing, more daunting than the prospect of fighting a powerful enemy, or even dying. It was the possibility of being left alone that terrified her. She might not understand it, when these two laughed. But it felt good just to hear it. The messenger stood a little straighter as Athaclena turned back to speak to her. "I will want to hear Lieutenant Benjamin's report personally. Would you please also give my compliments to Dr. Soo and ask her to join us in the operations chamboutdoor advertising bannerser?" "Yesser!" The chimmie saluted and took off at a run. "Robert?" Athaclena asked. "Your opinion will be welcome." He looked up, a distant expression on his face. "In a minute, Clennie. I'll check in at operations. There's just something I want to think through first." "All right." Athaclena nodded. "I'll see you soon." She turned away and followed the messenger down a water-carved corridor lit at long intervals by dim glow bulbs and wet reflections on the dripping stalactites. Robert watched her until she was out of sight. He thought in the near-total quiet. Why are the Gubru persisting in gassing the mountains, after nearly every human has already been driven out? It must be a terrific expense, even if their gasbots only swoop down on places where they detect an Earthling presence. And how are they able to detect buildings, vehicles, even isolated chims, no matter how well hidden? Right now it doesn't matter that they've been dosing our Surface encampments. The gasbots are simple machines and don't know we're training an army in this valley. They just sense "Earthlings!"-then dive in to do their work and leave again. But what happens when we start operations and attract attention from the Gubru themselves? We can't afford to be detectable then. There was another very basic reason to find an answer to these questions. As long as this is going on, I'm trapped down here!outdoor advertising banners Robert listened to the faint plink of water droplets seeping from the nearest wall. He thought about the enemy. The trouble. on Garth was clearly little more than a skirmish among the greater battles tearing up the Five Galaxies. The Gubru couldn't just gas the entire planet. That would cost far too much for this backwater theater of operations. So a swarm of cheap, stupid, but efficient seeker robots had been unleashed to home in on anything not natural to Garth . . . anything that had the scent of Earth about it. By now nearly every attack dosed only irritated, resentful chims- immune to the coercion gas-and empty buildings all over the planet. It was a nuisance, and it was effective. A way had to be found to stop it. Robert pulled a sheet of paper from a folder at the end of the table. He wrote down the principal ways the gasbots might be using to detect Earthlings on an alien planet. OPTICAL IMAGING BODY HEAT INFRARED SCAN RESONANCE PSI REALITY TWIST Robert regretted having taken so many courses in public administration, and so few on Galactic technologies. He was certain the Great Library's gigayear-oloutdoor advertising bannersd archives contained many methods of detection beyond just these five. For instance, what if the gasbots actually did "sniff out" a Terran odor, tracing anything Earthly by sense of smell? No. He shook his head. There came a point where one had to cut a list short, putting aside things that were obviously ridiculous. Leaving them as a last resort, at least. The rebels did have a Library pico-branch he could try, salvaged from the wreckage of the Howletts Center. The chances of it having any entries of military use were quite slim. It was a tiny branch, holding no more information than all the books written by pre-Contact Mankind, and it was specialized in the areas of Uplift and genetic engineering. Maybe we can apply to the District Central Library on Tanith for a literature search. Robert smiled at the ironic thought. Even a people imprisoned by an invader supposedly had the right to query the Galactic Library whenever they wished. That was part of the Code of the Progenitors. Right! He chuckled at the image. We'll just walk up to Gubru occupation headquarters and demand that they transmit our appeal to Tanith, ... a request for information on the invader's own military technology! They might even do it. After all, with the galaxies in turmoil the Library must be inundated with queries. They would get around to our request eventually, maybe sometime in the next century. He looked over his list. At least these were means he had heard of or knew something about. Possibility one: There might be a satellite overhead with sophisticated optical scanning capabilities, inspecting Garth acre by acre, seeking out regular shapes that would indicate buildings or vehicles. Such a device could be dispatching the gasbotsoutdoor advertising banners to their targets. Feasible, but why were the same sites raided over and over again? Wouldn't such a satellite remember? And how could a satellite know to send robot bombers plunging down on even isolated groups of chims, traveling under the heavy forest canopy? The reverse logic held for infrared direction. The machines couldn't be homing in on the target's body heat. The Gubru drones still swooped down on empty buildings, for instance, cold and abandoned for weeks now. Robert did not have the expertise to eliminate all the possibilities on his list. Certainly he knew next to nothing about psi and its weird cousin, reality physics. The weeks with Athaclena had begun to open doors to him, but he was far from being more than a rank novice in an area that still caused many humans and chims to shudder in superstitious dread. Well, as long as I'm stuck here underground I might as well expand my education. He started to get up, intending to join Athaclena and Benjamin. Then he stopped suddenly. Looking at his list of possibilities he realized that there was one more that he had left out. ... A way for the Gubru to penetrate our defenses so easily when they invaded. ... A way for them to find tts again and again, wherever we hide. A way for them to foil our every move. He did not want to, but honesty forced him to pick up the stylus one moroutdoor advertising bannerse time. He wrote a single word. .